// Random number generator - requires a PRNG backend, e.g. prng4.js

// For best results, put code like
// <body onClick='rng_seed_time();' onKeyPress='rng_seed_time();'>
// in your main HTML document.

var rng_state
var rng_pool
var rng_pptr

// Mix in a 32-bit integer into the pool
function rng_seed_int(x) {
  rng_pool[rng_pptr++] ^= x & 255
  rng_pool[rng_pptr++] ^= (x >> 8) & 255
  rng_pool[rng_pptr++] ^= (x >> 16) & 255
  rng_pool[rng_pptr++] ^= (x >> 24) & 255
  if (rng_pptr >= rng_psize) rng_pptr -= rng_psize
}

// Mix in the current time (w/milliseconds) into the pool
function rng_seed_time() {
  rng_seed_int(new Date().getTime())
}

// Initialize the pool with junk if needed.
if (rng_pool == null) {
  rng_pool = new Array()
  rng_pptr = 0
  var t
  if (window.crypto && window.crypto.getRandomValues) {
    // Use webcrypto if available
    var ua = new Uint8Array(32)
    window.crypto.getRandomValues(ua)
    for (t = 0; t < 32; ++t) rng_pool[rng_pptr++] = ua[t]
  }
  if (navigator.appName == 'Netscape' && navigator.appVersion < '5' && window.crypto) {
    // Extract entropy (256 bits) from NS4 RNG if available
    var z = window.crypto.random(32)
    for (t = 0; t < z.length; ++t) rng_pool[rng_pptr++] = z.charCodeAt(t) & 255
  }
  while (rng_pptr < rng_psize) {
    // extract some randomness from Math.random()
    t = Math.floor(65536 * Math.random())
    rng_pool[rng_pptr++] = t >>> 8
    rng_pool[rng_pptr++] = t & 255
  }
  rng_pptr = 0
  rng_seed_time()
  //rng_seed_int(window.screenX);
  //rng_seed_int(window.screenY);
}

function rng_get_byte() {
  if (rng_state == null) {
    rng_seed_time()
    rng_state = prng_newstate()
    rng_state.init(rng_pool)
    for (rng_pptr = 0; rng_pptr < rng_pool.length; ++rng_pptr) rng_pool[rng_pptr] = 0
    rng_pptr = 0
    //rng_pool = null;
  }
  // TODO: allow reseeding after first request
  return rng_state.next()
}

function rng_get_bytes(ba) {
  var i
  for (i = 0; i < ba.length; ++i) ba[i] = rng_get_byte()
}

function SecureRandom() {}

SecureRandom.prototype.nextBytes = rng_get_bytes
